  The silkworm eggs came in a very small box. They were sent by a friend of Uncle George’s who lived in the south of England. The eggs were stuck to pieces of paper in scattered groups. Some pieces of paper had only one or two eggs on them, others had as many as forty. They were small, round things, flattened on the top, and coloured light green. They reminded the boys of small mustard seeds, but they were not so round. In answer to Frank’s question as to why the eggs were laid in irregular groups, Uncle George answered: “When the silk-moth emerges from her pupa case, she lays her eggs anywhere on the floor of her cage. As the eggs are coated with a gluey material when newly laid, they stick firmly to the floor. “Those people who rear silkworms always have a sheet of clean paper covering the floor of the cage before egg-laying commences. After the eggs are laid, they are found adhering to this sheet of paper. The paper is taken out of the larva cage, and those parts containing eggs are cut out with scissors.” “How many eggs are laid by one moth,” Frank asked. “From four to five hundred,” his uncle replied. “Let us get our larva cage cleaned out, and we will put these eggs in the lower part of it and await their hatching.” “Why in the lower part,” Frank asked, as he set about cleaning the cage. “Because its floor is a drawer which can be pulled out. If you put them in the upper part, you must lay a sheet of paper on the floor first, for your silkworms must not be handled on any account.” “And how long do we have to wait for these eggs to hatch?” asked Tom. Larva Case. “That depends altogether upon the amount of warmth they receive, Tom. They will remain unhatched ever so long if kept in a cool place; but whenever they are placed where they can get the necessary amount of warmth, they begin to hatch. Let us put them in the front window, where they can get most sunshine.” About a week after the larva cage was placed in the window, Frank reported to his uncle that some of the eggs had turned white. “Take your lens and examine carefully those eggs which have lost their colour,” said Uncle George. Lifting out one of the small pieces of paper with eggs on it, Frank examined it with the glass. “Oh,” he said, “these colourless eggs are just empty shells, and there are two small creatures crawling along the edge of the paper. How small they are! They are no longer than the breadth of a pin-head. They are almost black in colour, covered all over with hair, and have very large heads.” “Well, these are newly-hatched silkworms,” said Uncle George, “and they are already looking for food. Run out to the garden and bring in some fresh lettuce leaves.” Uncle George carefully dried the lettuce leaves before putting them into the cage. In two days all the eggs were hatched, and in their place were as many black, hairy, crawling little creatures with clumsy heads. Although they did not seem to eat much, they grew very rapidly. When three days old, they were fully twice as big as when hatched. In five days the silkworms seemed to have increased in number as well as in size. In fact, there seemed to be twice as many grubs as there were of eggs. Then Uncle George explained that half of these were not grubs, but simply empty skins. “The silkworm, in order to grow, must cast its skin,” he said. “It does this four times during its lifetime. Look out for another moult, or skin-casting, in four days’ time.” Four days later the grubs cast their skins again, just as Uncle George had said. They were now about half an inch in length, and much lighter in colour. In six further days they moulted a third time. Instead of dingy, hairy grubs, they were now hairless caterpillars, Silk Moth.
“They are full grown now, boys,” said Uncle George, “and will soon begin to spin their silken cocoons. “They are now about three inches long, and very different from the tiny hairy grubs which came out of the eggs over a month ago.” “We have been comparing drawings of them with drawings we made of the caterpillar of the white cabbage “That is good,” said Uncle George. “They are, indeed, very much alike. The body is made up of thirteen segments, and they have the same number of legs. They differ from the cabbage caterpillar, however, in size and colour. Notice the little horn which sticks up out of the twelfth segment. Your cabbage caterpillar did not have that. If you look closely you will notice a long silk thread issuing from the head of one of these silk-spinning caterpillars. This one has just begun to make his cocoon; and, in order to prevent his threads becoming entangled with those of the other caterpillars, I will place this small paper cone over him.” Next day Uncle George covered several of the caterpillars with paper cones. On the roof of the cage the boys saw one caterpillar surrounded with a flimsy web of silk of a golden-yellow colour. As they watched the creature turning its head round and round inside the silky veil, their uncle told them that the creature was spinning silk at the rate of about a foot per minute. In three days each caterpillar had surrounded itself with a dense silken cocoon as large as a walnut. Then Uncle George took one of the cocoons, and, cutting it open, showed the boys the brown, shining chrysalis inside. He took another cocoon, and, having dipped it into warm water, began to wind the silken thread on to a piece of card. Both Frank and Tom were amazed at the length of this silken thread. They were more surprised when they “Tell us, please, Uncle George,” said Frank, “why the creature spins all this silk, and how it makes it?” “You are asking a difficult question,” said his uncle, “but I will tell you something about it.
“The creature spins this cocoon to protect its chrysalis, of course. The silk is produced in two long, coiled tubes, which occupy nearly the whole length of the creature’s body. “Silk, before it issues from the caterpillar’s body, is a fluid. Whenever it comes out into the air, it becomes horny. Two strands are produced at once—one from each of the long coiled tubes. Before they leave the caterpillar’s body they are pressed together to form one flat, ribbon-like thread. Silk is one of the strongest fibres in the world. It is nearly as strong as steel, and much stronger than many of our metals. “In a fortnight your silken cocoons will produce white, fluffy moths. ‘Then you can supply your friends with hundreds of ‘silkworm’ eggs, and still have enough over to stock your larva cage.” Silk Moths—Male and Female. Exercises on Lesson XIV.
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